1. Field of the Invention
The invention relates generally to hand tools and more specifically to clamping tools.
2. Description of Prior Art
C-clamps, used as a portable vise, for temporarily joining work pieces have been around for centuries, but in all that time the tool has progressed very little from its original design, structure and function. Primarily because its plunger is threaded, the conventional c-clamp is slow and awkward to use. Normal operation requires the work pieces to be staged, the clamp to be adjusted to approximate clamping distance, the work pieces to be staged for the final time, and the clamp then secured on the material, often with the help of a third hand from a friend. This process can be quite difficult when work pieces are heavy and tedious repetitive handling can be very strenuous.
Recently, an improved, alternative c-clamp has evolved, which makes this "friend" obsolete by providing a one handed advancing mechanism for the threaded plunger. Unfortunately, this one handed model appears to create more problems than it solves. First, like its ancestor, the one handed model uses a threaded plunge that advances slowly, requiring the work pieces to be staged, the clamp to be set at the approximate distance, the material to be staged again and the clamp then secured on the work pieces--this can be a distinct disadvantage when clamping heavier work pieces that must be held in place until the clamp is secured.
Second, the mechanism advancing the plunger extends beyond the clamp structure, becoming a potential obstacle that interferes with the staging and securing of the work pieces.
Third, because its driving mechanism is complicated in design and relies on many parts to advance the plunger, the existing one-handed c-clamp is expensive to manufacture.
Existing prior patents which may be pertinent to this invention are as follows:
______________________________________ R. L. Irelan 4,436,294 Mar. 13, 1984 P. J. Y. Chang 4,081,112 Mar. 28, 1978 J. Y. Wang 4,582,307 Apr. 15, 1984 ______________________________________
Though it teaches a device incorporated in the c-clamp structure to facilitate the rapid advancement and retraction of the threaded plunger, the Wang patent still requires two hands for operation, thus requiring repeated handling of the work pieces and the clamp itself. The Irelan patent is the only one listed showing a one-handed design used in combination with a c-clamp type structure, but, as explained above, the threaded plunger slows operation and the complicated advancing mechanism protrudes outside the clamp body. Chang discloses a similar advancing mechanism, but here again, there is no economy in the space needed outside the body of the tool. No prior invention combines the advantages provided by a plunger that has a smooth surface and a threaded shaft.